# What's New

View new features for AcuSolve 2021.2.

## Altair AcuSolve 2021.2 Release Notes

### New Features

Porous Media Physical Velocity
Filter media and other flow-through components are often modeled in larger domains as simple porous media with a known pressure-drop-to-velocity ratio. While the intricacies of the flow through the tortuous paths around fibers, tube bundles, and other solid obstructions is sometimes ignored, you will occasionally be interested in a more physical representation of the flow within these components. Flow in the normal direction through a porous medium, as viewed by an observer, is referred to as the Superficial Velocity; or the relative decrease in velocity in the original flow direction that corresponds to the assigned pressure drop. As the flow travels through the physical medium, however, it has the potential to accelerate in directions orthogonal to the original incoming flow direction. These more physical results using Physical Velocity are now available for output from AcuSolve.
Topology Optimization
AcuSolve integrated optimization capability grows yet again with the addition of topology optimization. Find your optimum shape by simply defining inlets, outlets, and the allowable space in which the solver can work. AcuSolve’s gradient-based topology optimization method will quickly and efficiently find the path of least resistance to deliver your fluid with minimal effort.
EDEM/AcuSolve: Non-spherical Particle Lift Models
Speed, robustness, and accuracy, three qualities that AcuSolve has enjoyed for years. As AcuSolve integrates further with Altair EDEM, accurate representation of individual particles within the fluid domain becomes even more important. To support this AcuSolve has added two new lift models for non-spherical particles. The first model, nonspherical_lift, is the aerodynamic lift force arising from the particle incidence angle. The second model, Saffman_Magnus_nonspherical_lift, incorporates the lift effect of shear flow and rotation in addition to the aerodynamic lift force due to particle incidence angle.
EDEM/AcuSolve: Non-spherical Particle Torque Model
As AcuSolve/EDEM coupling continues to evolve and grow to support more and more physically accurate scenarios the particles modeled become less and less standard, or spherical. As particles in an airstream become less spherical the impact of torque on the particle due to the surrounding airflow becomes greater. You can now accurately account for the torque experienced by high aspect ratio, low sphericity particles. Methods for modeling torque due to pitching, torque due to rotation, and torque due to the combination of pitching and rotation are all now available.
EDEM/AcuSolve: Scaling factor for Lift and Drag
Particle counts in large industrial models can occasionally become quite large. Modeling each individual particle in these scenarios can also become quite expensive. To alleviate the large computational cost while still running large industrial models AcuSolve/EDEM coupling now allows for scaling of lift and drag forces. With this capability single particles in EDEM can now represent a collection of many smaller physical particles. Modeling the collection of many physical particles directly as a single particle in EDEM with equivalent mass and volume typically results in larger lift and drag forces than desired. The scaling factor mitigates this condition.
EDEM/AcuSolve: Particle Mass Transfer
The purpose of coupling solvers is to include the physics modeling that each does best. One of AcuSolve’s many strengths is in the accurate modeling of heat transfer and extending its capability to include mass transfer at a particle boundary is a natural progression. With AcuSolve 2021.2 you will be able to model the accumulation of spray on particles in an EDEM simulation and the evaporation of the water content of the accumulated spray during an AcuSolve/EDEM coupled simulation.

### Enhancements

Negative Density reported in Log file
The AcuSolve Log file now includes a short list of coordinate locations indicating points where the solver returns negative density values. This is typically encountered when variable density models are used, and the overall model setup is not quite synchronized. The location information is helpful to give you an idea of where to look in the model to correct boundary or operating conditions. If the number of locations is greater than five, more information about the total number of points where density is negative is also reported.
Utility programs
• AcuMakeDLL, used to compile and link user-defined functions on Windows, will automatically search for Enterprise, Professional, and Community versions of MicroSoft Visual Studio. AcuSolve supports versions of Visual Studio up through version 2019.
• AcuCpOutFiles, a script which copies the minimum number of files allowing you to process output data, is now available on Windows and Linux platforms.
• AcuCpRstFiles, a script which copies the minimum number of files allowing you to restart from an earlier simulation, is now available on Windows and Linux platforms.
The following new tutorials have been added for the HyperWorks CFD interface:
• ACU-T: 2300: Atmospheric Boundary Layer Problem – Flow Over Building
• ACU-T: 3110: Exhaust Manifold Conjugate Heat Transfer - CFD Data Mapping using acuOptiStruct
• ACU-T: 4002: Sloshing of Water in a Tank
• ACU-T: 5403: Piezoelectric Flow Energy Harvester: A Fluid-Structure Interaction
• ACU-T: 6105: Single Particle Sedimentation – Effect of Lift and Torque
• ACU-T: 6106: AcuSolve - EDEM Bidirectional Coupling with Mass Transfer
• ACU-T: 6501: Flow Through Porous Medium with Physical Velocity
The following six validation cases have been updated to the HyperWorks CFD platform:
1. Turbulent Flow Over a Backward-Facing Step
2. Turbulent Flow with Separation in an Asymmetric Diffuser
3. Turbulent Flow Past a Convex Curve in a Channel
4. Turbulent Flow Through a 180 Degree Curved Channel
5. Turbulent Mixing Layers in an Open Channel
6. Laminar to Turbulent Transition Over an Airfoil
• In the Command Reference Manual, the default value of the outflow_type parameter under SIMPLE_BOUNDARY_CONDITION was corrected to be auto_pressure instead of pressure.
• In the Command Reference Manual, clarification regarding the usage of the from_directory option of the RESTART command has been added.
• In the Command Reference Manual, the default value of 273.15 for convective heat reference temperature has been updated.
• In the Programs Reference Manual, documentation has been added for the AcuGetNodeSubset script command options.
• In the Programs Reference Manual, the description for HTC Method 2 of AcuTherm has been improved.
• In the User-Defined Functions Manual, Global Routines section, the function name of udfGetMmoRgdJac() has been corrected.

### Known Issues

The following known issues will be addressed in a future release as we continuously improve performance of the software:
• Legacy support for AcuConsole GUI is not supported on Linux versions of RHEL/CentOS higher than 7.5 and SLES versions higher than 15.
• Users on platforms later than RHEL/CentOS 7.5 or SLES 15 are encouraged to use the Altair Compute Console interface for launching simulations.
• AcuSolve users using the HyperWorks CFD user interface should update both solver and GUI to version 2021.2 together.

### Resolved Issues

• Thermal shell creation on floating, non-manifold surfaces is now working correctly.
• An issue with thermal shell definition which prevented post-processing of data has been corrected.
• An error with the AcuTrans “-dir” option, to specify a working directory other than the current directory, has been fixed.
• An issue where parallel jobs using Intel MPI were being overloaded on a single host has been corrected.
• An error with AcuPlotData correctly plotting fft data has been resolved.
• ACU-T: 4001 and 4002: Missing Steps have been added to assign material properties.
• ACU-T: 4003: Steps to define nodal initial conditions have been added.
• ACU-T: 4100: Text has been added indicating that the carrier field must be the heavier fluid.
• ACU-T: 5000: Steps demonstrating the creation of monitoring surfaces have been added.
• ACU-T: 5201: Steps to launch the coupling via Altair Compute Console have been added.
• ACU-T: 6104: A screen shot of a table of particle sizes has been updated.
• ACU-T: 6010 was renumbered to ACU-T: 6500 for v2021.1.

## Altair AcuSolve 2021.1 Release Notes

### New Features

EDEM 2-way Coupling for Non-Spherical Particles
The AcuSolve/EDEM coupling capability for simulating particle flows is extended yet again with additional support now available for non-spherical particles. Sphericity and aspect ratio values can be specified for the variety of particle types in the simulation. In addition, the Haider-Levenspiel, Holzer-Sommerfeld, and Ganser drag coefficient models are now available. As particles come in many shapes and sizes so should your modeling options.

### Enhancements

Inviscid Compressible Flow
You can now run inviscid compressible flow simply by using the compressible_euler option for the flow equation. Selecting this convenience option will deactivate turbulence and zero out material viscosity and conductivity.
Time-Varying Translation
When defining translational motion that varies with time a new option is available when using multiplier functions. The new parameter multiplier_function_on_time will allow you to directly define the changes in translational speed as a function of time in their MULTIPLIER_FUNCTION command. An example is shown below.
MULTIPLIER_FUNCTION ( “time-varying translation” ) {
Type			    = piecewise_linear
Curve_fit_variable	    = time
Curve_fit_values		= {0.0, 0.0; 1.0, 5.0; 2.0, 3.0; }
}
MESH_MOTION ( “Translational Motion” ){
Type					        = translation
Translation_variable 			    = multiplier_function_on_time
translation_variable_multiplier_function	= “time-varying translation”
}
User-Defined Functions
Density is now available through the UDF_NBC_DENSITY parameter from the udfGetNbcData() and udfGetNbcAuxData() functions.
Utility programs
• In the AcuPlotData utility you now have the option to invert the x- or y-axis independently with the -x_invert and -y_invert options, respectively. This can be very useful when creating Cp plots of airfoil data. By default, these parameters are inactive.
• The Acu3DShapes utility now supports 3 types of symmetry for morph shape construction. Circular (full), Circular (periodic), and Planar.
• The AcuGetNodeSubset utility is now available on the Windows platform.
The following new tutorials have been added for the HyperWorks CFD interface.
• ACU-T: 6103: AcuSolve-EDEM Bi-Directional coupling with Heat Transfer
• ACU-T: 6104: AcuSolve-EDEM Bi-Directional coupling with Non-Spherical Particles
• ACU-T: 7100: DOE Study of an HVAC Duct (workflow includes Inspire Studio and HyperStudy interfaces)
The following 12 validation cases have been updated to the HyperWorks CFD platform:
1. Single-Phase Nucleate Boiling in a Rectangular Channel
2. Turbulent Flow Behind an Open-Slit V
3. Turbulent Natural Convection Inside a Tall Cavity
4. Turbulent Flow Over a NACA 0012 Airfoil
5. Flow Between Concentric Cylinders
6. Natural Convection in a Concentric Annulus
7. Separated Laminar Flow Over a Blunt Plate
8. Heat Transfer Between Radiating Concentric Cylinders
9. Heat Transfer Between Radiating Concentric Spheres
10. Circumferential Flow in a Cylinder Induced by a Rotating Solid
11. Oscillating Laminar Flow Around a Circular Cylinder
12. Multiphase Flow of a 2D Dam Break
• In the Command Reference Manual documentation has been added for the MOMENTUM_SOURCE command and for cylindrical anisotropic conductivity under the MATERIAL_MODEL command.
• The field_flux and convective_field_flux variables have been added to the AcuTrans documentation under integrated surface output and nodal surface output.

### Known Issues

The following known issues will be addressed in a future release as we continuously improve performance of the software:
• Visualization of models with thermal shells defined on floating, non-manifold surfaces is not working.
• Legacy support for AcuConsole GUI is not supported on Linux versions of RHEL/CentOS higher than 7.5 and SLES versions higher than 15.
• Users on platforms later than RHEL/CentOS 7.5 or SLES 15 are encouraged to use the Altair Compute Console interface for launching simulations.

### Resolved Issues

• Issues with OptiStruct Direct Coupling have been resolved for both Structural and Thermal coupling.
• An issue with the output of UDF_OSI_TEMPERATURE has been corrected.
• The default reference temperature for reference_temperature under the DENSITY_MODEL and ELEMENT_BOUNDARY_CONDITION commands, opening_temperature under the RADIATION_SURFACE and SIMPLE_BOUNDARY_CONDITION commands, and convective_heat_reference_temperature under the SIMPLE_BOUNDARY_CONDITION command is now consistent at 273.15.
• User-specified species names are now reflected in output from AcuTrans and when post-processing in HyperView and AcuFieldView via binary file read.

## Altair AcuSolve 2021 Release Notes

### New Features

Compressible Flow
AcuSolve now delivers the ability for users to simulate subsonic, transonic, and supersonic flows. Speeds of up to Mach 1.5, including shocks and expansions, are solved with minimal Courant-Friedrichs-Lewy (CFL) constraints using the compressible Navier-Stokes equations option. Compressible flow is compatible with all currently available single-phase features including turbulence models and mesh motion. The Sutherland viscosity and conductivity material models have been added as well. Nodal output data for compressible flow include density and Mach number. Total pressure and total temperature are added to Derived Quantity output.
EDEM 2-way Coupling
AcuSolve multiphysics capabilities are extended with the addition of bi-directional coupling with EDEM. Currently, users can couple EDEM and AcuSolve through sequential steady, sequential transient, and now full two-way transient coupling. Additionally, particles much larger than the mesh size are permitted. Heat transfer is now supported for particle-particle, fluid-particle, and solid-particle interactions and all mesh motion functionality can be used in EDEM-coupled runs.
Multiphase Improvements
Contact angle calculations now provide additional accuracy of liquid free surfaces in immiscible multiphase calculations and the behavior of liquid droplets on hydrophilic or hydrophobic solid surfaces can be modeled as well.
GPU Acceleration
The temperature_flow equation is now supported on GPU.
Altair Compute Console
The Altair Compute Console (ACC) is the easiest way to launch an AcuSolve simulation. It includes an interactive GUI for selecting input files, defining run options, submitting multiple solver runs using a queue, scheduling a delay, stopping a job, and has all the environment variables needed to run AcuSolve predefined. ACC help can be launched from within the software as well.

### Enhancements

Evaporation mass flux
Quantify the condensation and evaporation of water vapor on a surface when using the humid air model. The integrated value of field_flux for Humid Air provides the rate of mass transfer to or from a surface in units of mass/time. A positive value indicates condensation and a negative value indicates evaporation.
Carreau-Yasuda viscosity model
The temperature-dependent Carreau-Yasuda viscosity model is now available.
Total temperature
Total temperature is now available for the OSI, OEI, OSS, and OES output types.
Two new variables, radiative_heat_flux (OSF) and surface_radiative_heat_flux (OSI), have been added for the discrete ordinate radiation model. These variables allow the user to quantify the contribution of radiation heat transfer on a surface.
Backflow reported
Reversed flow at inlets and outlets is now quantified and reported to the user in the Log file at runtime.
Utility programs
The AcuLiftDrag and AcuGetCpCf utilities now accept wild cards when specifying surface names. The AcuInterp and AcuPlotData utilities are now available on the Windows platform.
New SimLab tutorials have been added for the Heat Exchanger Component (ACU3300/SL2150) and the Rigid Body Check Valve (ACU5200/SL2330).
New HyperWorks CFD tutorials have been added for Supersonic Converging-Diverging Nozzle (ACU2400), Sequential Transient Coupling with EDEM (ACU6101), Bi-Directional Coupling with EDEM (ACU6102), and Contact Angle (ACU4003).
Existing tutorials for Porous Media (ACU6010), Humidity (ACU4200), Condensation/Evaporation (ACU4201), DO (ACU3203) and P1 (ACU3202) Radiation, and Sliding Mesh (ACU5001) have also been added for the HyperWorks CFD interface.
A new validation case of the Sajben diffuser has been added for compressible flow.
In the Command Reference Manual documentation of two forms of definition under Specific Heat have been added, namely, piecewise_bilinear_enthalpy and piecewise_polynomial_enthalpy. The Sutherland viscosity and conductivity models and Carreau-Yasuda viscosity model have been added as well. In the Program Reference Manual documentation has been added for the Altair Compute Console, Element Statistics Output, AcuGetCpCf, AcuInterp and AcuPlotData.

### Known Issues

The following known issues will be addressed in a future release as we continuously improve performance of the software:
• Legacy support for AcuConsole GUI is not supported on Linux versions of RHEL/CentOS higher than 7.5 and SLES versions higher than 15.
• On Windows platforms, inputs to AcuInterp and AcuPlotData should be given in double quotes, not single quotes.
• On Windows platforms, solid lines do not display correctly when plotted to .png format from AcuPlotData. Note that when writing to .pdf format solid lines display correctly.

### Resolved Issues

• A conflict with AcuTrace particles and auto_wall surfaces has been resolved.
• Memory management on AMD platforms has been improved.
• The incident_radiation variable reference was missing in the AcuTrans documentation.
• Various typos were corrected in the ACU-T3110 and ACU-T3311 tutorials.
• In the Programs Reference Manual odgen was corrected to ogden.